1. Field of the Invention
The present invention relates to a dielectric device including a dielectric layer, and to a method for producing the dielectric device.
2. Description of the Related Art
A variety of dielectric devices of this type have conventionally been known. Generally, such a dielectric device includes, in addition to a dielectric layer, a predetermined substrate, a lower electrode layer, and an upper electrode. The lower electrode layer is formed on the substrate. The dielectric layer is formed on the lower electrode layer. The upper electrode is formed on the dielectric layer. The dielectric layer is formed by subjecting the lower-electrode-layer-formed substrate to film formation through, for example, the screen printing process, the green sheet process, aerosol deposition method, or powder jet deposition method.
The screen printing process is a technique in which a substrate is coated, through screen printing, with a slurry prepared by dispersing ceramic powder in a solvent containing an organic binder, and the resultant coating film is sintered at a high temperature of 900° C. or higher, to thereby form a dielectric layer. The green sheet process is a technique in which a thick film having a predetermined thickness is formed from the aforementioned slurry, followed by drying, thereby yielding a green sheet; the green sheet is subjected to a predetermined machining process such as cutting or drilling; and the resultant green sheet is sintered at a high temperature in a manner similar to that described above, to thereby form a dielectric layer. Aerosol deposition method is a technique in which an aerosol is formed by dispersing powder in a gas through, for example, vibration; the thus-formed aerosol is conveyed to a deposition chamber which has been evacuated to a predetermined level; and the aerosol is sprayed through a nozzle onto a predetermined substrate, to thereby form a dielectric layer. Powder jet deposition method is a technique in which powder is conveyed by means of high-pressure gas, and is sprayed, at high speed, through a nozzle to a substrate provided in air, to thereby form a dielectric layer.
Typical examples of the aforementioned dielectric device include a piezoelectric actuator and an electron emitter.
A piezoelectric actuator is configured such that when a predetermined electric field is applied to a dielectric layer through application of a predetermined voltage between a lower electrode layer and an upper electrode, the dielectric layer can be deformed. For example, Japanese Patent Application Laid-Open (Kokai) No. 2002-217465 discloses a unimorph-type piezoelectric actuator including a substrate and a dielectric layer bonded thereonto, the actuator being configured such that the substrate can be bent or deformed through expansion and contraction of the dielectric layer through the transverse piezoelectric effect.
Meanwhile, an electron emitter is configured such that it can be suitably employed as an electron beam source in a variety of apparatuses that utilize electron beams, including a display (e.g., a field emission display (FED)), an electron beam irradiation apparatus, a light source, an electronic-component-manufacturing apparatus, and an electronic circuit component.
Such an electron emitter (i.e., a type of the aforementioned dielectric device) includes an emitter section which is provided in a reduced-pressure atmosphere having a predetermined vacuum level. The emitter section, which includes a dielectric layer, is configured such that it can emit electrons into the reduced-pressure atmosphere through application of a predetermined driving electric field between a lower electrode layer and an upper electrode. Conventionally known electron emitters of this type include those disclosed in Japanese Patent Application Laid-Open (Kokai) No. 2005-183361 and the specification of U.S. Patent Application Publication No. 2006/0012279.
Such an electron emitter (i.e., a type of the aforementioned dielectric device) is operated as follows. Firstly, in the first stage, voltage is applied between an upper electrode and a lower electrode layer so that the upper electrode is higher in electric potential. An electric field generated by the applied voltage brings the emitter section of the electron emitter into a predetermined polarization state.
Subsequently, in the second stage, voltage is applied between the upper electrode and the lower electrode layer so that the upper electrode is lower in electric potential. Through this voltage application, the polarization of the emitter section is inverted, and electrons are accumulated on an electron emission region.
Subsequently, in the third stage, voltage is again applied so that the upper electrode is higher in electric potential. Through this voltage application, the polarization of the emitter section is re-inverted. With this polarization inversion, the electrons accumulated on the electron emission region are emitted from the emitter section by means of electrostatic repulsion between the electrons and dipoles, and the thus-emitted electrons fly in the aforementioned reduced-pressure atmosphere.